The present invention relates to an automatic transmission.
Heretofore, there is known an automatic transmission using a mechanism of a conventional manual transmission, that is, mesh gear type transmission as the transmission device, which is provided with a clutch for engaging and disengaging the engine with the transmission, and an actuator for moving the clutch for engaging and disengaging each gear with the output shaft, and which performs automatic shifting by controlling hydraulic pressure to the actuator for performing engagement and disengagement of the clutch.
In a conventional automatic transmission thus constituted, there exists a condition where the cogged clutch is engaged to none of the gears, that is, a neutral condition.
In such neutral condition, in the case where the gear is shifted from the 1st gear to the 2nd gear, from the 2nd gear to the 3rd gear, from the 3rd gear to the 4th gear, and from the 4th gear to the 5th gear, the driver feels a state of shock as if the vehicle has decelerated, even when the vehicle is accelerating, because the acceleration power is not transmitted during neutral condition. This results in poor drivability.
The object of the present invention is to provide an automatic transmission that moderates the shock originated at engagement and disengagement of the clutch during acceleration.
In order to achieve the above-mentioned object, the present invention provided an assist mechanism for transmitting rotational force of an input shaft to an output shaft, in the period when no cogged clutch other than a starting clutch is engaged with any of a plurality of shift gears, during switching of the cogged clutch.
According to another aspect of the present invention, an assist mechanism for transmitting rotational force of the input shaft to the output shaft, by transmitting rotation of an assist shaft rotated by the rotation of a counter shaft to the output shaft via an assist gear, in the period when the gear currently engaged is disengaged and a new gear is to be engaged, during shifting. The assist mechanism is preferably provided so that the assist shaft is deviated from a line connecting a central axis of the counter shaft rotated by the power of the input shaft, with a central axis of the output shaft which is engaged with the plurality of cogged clutches, is fit with the plurality of shift gears so as to rotate freely, and which outputs rotation of the counter shaft with the gear shifted according to need, and a central axis of the assist shaft is positioned below the central axis of the counter shaft.
According to still another aspect of the present invention, an assist mechanism for transmitting rotational force of the input shaft to the output shaft by the assist shaft, by transmitting rotation of the counter shaft to the assist shaft via the assist gear, in the period when the gear currently engaged is disengaged and a new gear is to be engaged during shifting, is provided inside a transmission case on the side of a gear oil injection hole, and is provided so that the assist shaft is provided to the position below a line perpendicular to a line connecting a central axis of the output shaft with a central axis of the counter shaft at the center of said output shaft.
According to still another aspect of the present invention, an assist mechanism for transmitting rotational force of the input shaft to the output shaft by the assist shaft, by transmitting rotation of the counter shaft to the assist shaft via the assist gear, in the period when the gear currently engaged is disengaged and a new gear is to be engaged during shifting, is provided so that the assist shaft is positioned on the opposite side of the output shaft relative to a horizontal line passing the center of the counter shaft.
According to still another aspect of the present invention, an assist mechanism for transmitting rotational force of the input shaft to the output shaft by the assist shaft, by transmitting rotation of the counter shaft to the assist shaft via the assist gear, in the period when the gear currently engaged is disengaged and a new gear is to be engaged during shifting, is provided to the position opposite to the side of the engine and the starting clutch, based on the position of the counter shaft.
According to still another aspect of the present invention, an assist mechanism for transmitting rotational force of the input shaft to the output shaft by the assist shaft, by transmitting rotation of the counter shaft to the assist shaft via the assist gear, in the period when the gear currently engaged is disengaged and a new gear is to be engaged during shifting, is provided so that the assist shaft is provided to the opposite side of the output shaft relative to a horizontal axis passing the center of the counter shaft, as well as to the position opposite to the side of the engine and the starting clutch, based on the position of the counter shaft.
Preferably, the assist mechanism starts engaging when a switch command for the cogged clutch is output, before the cogged clutch currently engaged with the shift gear is completely disengaged, engages according to torque of the engine and transmits rotational force of the input shaft to the output shaft, when the cogged clutch is completely disengaged from the engaged shift gear, and disengages when the cogged clutch is engaged with the shift gear to be engaged based on the switch command.
Preferably, the assist mechanism comprising the assist shaft rotating from the rotational force of the counter shaft, the assist input gear meshing with the counter assist gear fixed to the counter shaft and being mounted to the assist shaft so as to rotate freely, the assist output gear meshing with the counter gear of the highest gear mounted to the counter shaft so as to rotate freely and being fixed to the assist shaft, and the assist clutch for engaging the assist input gear with the counter shaft, transmits rotation of the assist input gear to the output shaft via the assist shaft and the assist output gear, based on an assist command.